My mower suddenly began running at a very high speed (an almost frightening high speed) which ran the battery down quickly. The noise level also reached something more like a gas powered mower. When the battery discharged while trying to mow, I attempted to remove it, but it would not disengage. In fact, the button used to disengage the battery also failed, rocking forward and out of position so that it would only raise the battery a fraction of the usual amount. Now the mower is useless. What to do?